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Attached herewith as Microfiche Appendix A is a microfiche of 468 pages of the computer program ladder flow chart of the present invention. The Microfiche Appendix contains 5 frames.
Astigmatism is a defect in the eye that is corrected by a lens with a non-spherical prescription. The prescription, which is usually expressed as cylinder on the patient""s prescription order, causes at least a portion of the surface of the lens to have the shape of a toric segment. Hence, such lenses are called toric lenses.
While the posterior surface of a contact lens is generally spherical in configuration, where the lens is to used to correct astigmatism it will have a toric configuration. That is, the curved portion of the posterior of the lens has a major and minor axis; the radius of curvature of the posterior surface of the lens being longer in the major-axis direction than in the minor-axis direction. The result is that rather than being of a spherical configuration, the posterior of the lens has a toric configuration with the major axis running orthogonal to the minor axis. The major diameter of the toric curve is generally smaller in diameter than the overall lens, and is cut into a starting base curve which has a spherical configuration.
The corrective lens must be properly oriented with respect to the eye of the wearer. That is, the intended top of the lens must be at the top of the wearer""s eye. For ordinary glasses this presents no problem, because the lens is permanently fixed to the frame at the correct rotational orientation. The ear and nose pieces of the frame assure that the frame and the lens do not rotate with respect to the wearer""s eyes. For contact lenses orientation is subject to constant alteration. In the case of contact lenses whose function is to correct astigmatism this is unacceptable.
Soft contact lenses which have been designed for use to correct astigmatism are well known in the art. Generally these lenses rely on some type of ballasting method to cause the lens to ride at the proper location on the eye. An ideal lens for correcting astigmatism has good rotational orientation. That is the intended top of the lens should be located at the top of the wearer""s eye when the lens is worn. A small amount of deviation from the correct orientation can be tolerated, provided the lens fitter measures the deviation and takes it into account in the lens""s prescription.
An ideal lens also provides for good rotational stability. That is, the lens should remain at a fixed rotational orientation within the eye during the entire wearing period. Furthermore, the lens should assume the same orientation each time it is worn. And, of course, the thinner the lens and the smoother the lens surface, the more comfortably the lens will feel to the wearer.
Lenses in accordance with this invention are preferably soft contact lenses, which may be formed of many materials including hydroxyethylmethacrylate, metallo-organic substances, silicone rubbers and various other materials such as described in U.S. Pat. Nos. 3,503,942 and 3,639,524. The preferred soft contact lenses are hydrophilic; that is, they absorb water and, in fact, the water becomes an integral part of their structure. Hydrophilic contact lenses made in accordance with U.S. Pat. No. 4,405,773 are especially preferred for practicing this invention.
Although contact lenses used for the correction of astigmatism have been around for some time, the costs to manufacture these lenses have not decreased over time. The cost has remained high due to the small number of lenses that are manufactured which is due, in part, to the many different number of lenses needed. For example, if toric lenses are rotationally configured for ballast variations of ten degrees, 36 different lenses may have to be manufactured to take into account the total number of lenses possible for each prescription. This is in contrast to one configuration needed for a non-toric lens. Further, since there are fewer astigmatic prescriptions than regular non-toric prescriptions, the number of toric lenses is even less than the 36-to-1 ratio disputed above.
The invention described herein provides a method of automatically manufacturing toric contact lenses which will greatly reduce the associated costs. By providing a precision, programmable, rotational alignment between the casting cups, toric lenses may be manufactured at similar speeds as non-toric lenses whereby a change in the toric prescription affords no down time of the manufacturing process. The automatic filling and closing machine obtains information about the toric lenses to be manufactured from the pallet containing the casting cups. After the information is communicated to the filling and closing machine, the programmable controller activates the filler and closer machine which then operates to manufacture a particular toric lens having a precise toric rotational alignment. Once a particular number of lenses are manufactured, the programmable controller will obtain new information from the next pallet tag and operate to rotate the casting cup assembly to a new rotational alignment thereby manufacturing toric lenses with a different toric rotational alignment. This process allows the manufacture of multiple toric lenses with different rotational alignments in the same or similar time it would take to make the same number of contact lenses with the same toric rotational alignment. Smaller batches of toric lenses can be manufactured in the same time it takes to manufacture a large batch of the same toric lenses.
It is an object of this invention to provide an apparatus that can accurately fill a molded casting cup with liquid monomer and reassemble the casting cup halves, i.e., front curve and base curve, under a precisely controlled motion while maintaining precision, programmable, rotational alignment between the casting cup halves.
It is another object of this invention to provide a method of manufacturing astigmatic or toric contact lenses by filling one-half of a molded contact lens casting cup with liquid monomer, and, using a programmable precision filling and closing apparatus, programmed such that the other half of the casting cup assembly is rotatably aligned close to the other half thereby manufacturing a toric contact lens.
It is another object of this invention to provide a method of automatically changing the rotational alignment of the casting cup assembly whereby a new prescription toric lens may be manufactured with zero loss down time or changeover time.
It is another object of this invention to provide a fully-automated printing system to accurately print axis orientation feature on the front of the contact lens such printing thereby aiding in the proper fitting and stability of the toric contact lens on the wearer""s eye.
It is another object of this invention to provide a method of automatically printing an accurate axis orientation feature on a toric lens by inserting a pallet containing toric contact lenses via a conveyor into the printing zone. Then using encoded information, the automatic printing apparatus applied the axis orientation mark to a silicone print pad, the location of the mark determined by the encoded information. Then, the contact lens is held in position so that the axis orientation feature or iris print can be applied. Finally, the casting cup is located for a video inspection, thereby verifying the location of the axis orientation feature on the casting cup.
These and other important features and advantages of the invention will become apparent when viewing the drawings and when described in the detailed embodiment of the invention below.